Hydrazine gel compositions containing metal and micro-dimensional fibers



United States Patent 3,301,721 HYDRAZINE GEL COMPOSITIONS CONTAINING METAL AND MICRO-DIMENSIONAL FIBERS Frederic C. McCoy, Beacon, and Edwin C. Knowles, Poughkeepsie, N.Y., assignors t0 Texaco Inc., New York, N.Y., a corporation of Delaware No Drawing. Filed Jan. 18, 1961, Ser. No. 83,581 18 Claims. (Cl. 149-2) This invention relates to compositions of matter comprising stable gels containing a high content of finely divided powders which are particularly useful as suspention-type high energy i uels. More particularly, this invention relates to stable gels containing up to 50 percent by weight of high energy powders such as aluminum.

It is well known that elements and compounds such as aluminum and boron carbide possess extremely high heats of combustion. There have been many eliorts to prepare suspensions of such powders in liquid vehicles in order to take advantage of the high heats of combustion of these materials and the ease of handling of such vehicles. Prior to this invention, it has not been possible to suspend high energy powders such as aluminum in a stable form in a vehicle such as hydrazine. A wide variety of suspending agents such as soaps and a large number of dispersants have been used and suggested without success in increasing the concentration of high energy powders suspended in high energy liquid vehicles.

The attractiveness of the high energy powders-hydrazine compositions as a high energy propellant stems from the fact that the powders can be selectively oxidized to yield large amounts of heat. This thermal energy decomposes the hydrazine to hydrogen and nitrogen, which, when expanded by the heat of combustion of the powders, provide a very attractive working gas for the propulsion of rockets and missiles. As an example, calculated specific impulse for the hydrazine-aluminum combination of the present invention is in the range of 260-280 seconds, using conventional oxidizers while the density specific impulse is in the range of 450480 seconds.

The stab-1e gels of this invention comprise to 50 weight percent of a material selected from the group consisting of aluminum, beryllium, magnesium, carbon, boron carbide and mixtures thereof, 0.1 to 3.0 weight percent micro-dimensional fibers having an average fiber diameter of less than 1 micron, a polymeric thickening agent present in an amount of 0.1 to 3.0 weight percent of the total gel composition and the remainder hydrazine.

In addition to the preferred hydrazine of the present invention dialkyl substituted hydrazine wherein the alkyl group contains one to three carbon atoms, may also be used. An example of such a composition is dimethyl hydrazine.

The micro-dimensional fibers which constitute 0.1 to 3.0 weight percent and the soluble polymeric thickening material also constituting 0.1 to 3.0 weight percent of the total gel are the key materials in the formation of stable hydrazine gels containing 10 to 50 weight percent powdered material. The excellent gelling efliciency of the micro-dimensional fibers and of thesoluble polymeric thickening agent provides the necessary suspending power for the large amount of powder employed in the compositions of this invention and results in gels which are of a soiit, easily fiowable consistency despite the fact that they contain up to 50 percent powdered elements or compounds.

The powders employed in the formation of the easily flowable smooth stable propellant gels of this invention are low atomic weight elements and compounds of such elements which have high heats of combustion on both a weight and volume basis. The powdered materials meet-- ing these requirements are aluminum, boron, beryllium, magnesium, carbon, boron carbide and mixtures thereof. Aluminum, boron, boron carbide and mixtures thereof are the preferred powders from the standpoint of availability and heat of combustion. Aluminum powder is widely used because of its low cost, ready availability in suitable powdered form and its high heat of combustion. Mixtures of aluminum and boron are also a preferred material for use in the formation of propellant gels because boron has approximately 60% higher heat of combustion than aluminum on a volume basis.

The prescribed; powders have a maximum particle size of 20 mesh in order to form the stable gels of this invention. The powdered particles are usually smaller than mesh with sizes of 200 to 350 mesh powders generally being utilizable. Powders of the spheroidal type have better packing properties, thus permitting more powder to fit into a given volume of vehicle. It appears, however, that there may be merit in using a mixture of flake and spheroidal type powders from a standpoint of long-time (months-years) storage stability. It is advantageous for the powders to contain a gradation in particle sizes below the prescribed maximum which permits the smaller particles to occupy the voids between the larger particles and the resultant formation of a denser gel.

The powdered material constitutes 10 to 50 weight percent of the stable gels of the present invention. In gels employed as propellants, the powders preferably constitute 30 to 50 weight percent of the total gel composition.

The micro-dimensional fibers employed as suspending agents of the finely divided powders are fibers which are insoluble and non-reactive with hydrazine and are primarily derived from glass, asbestos, cellulose and synthetic fibers. Examples of glass fibers useful as suspending agent in the present invention are conventional sodalime glass comprising sodium oxide, calcium oxide and silica boro silicate glass used in the formation of Pyrex equipment, soda lime quartz glass, lead glass and mixtures thereof. Examples of asbestos fibers that are useful as suspending agents in the present invention are the chrysotile form of asbestos, and other asbestos fibers that are insoluble and non-reactive with hydrazine. In addition many cellulose and synthetic fibers are also useful as suspending agents of the finely divided powders in the composition of the present invention. For example, cellulose, polytetrafluoroethylene, polyethylene and other fibers which are insoluble and non-reactive with hydrazine. Glass, cellulose and asbestos are the preferred fibers of the present invention.

The micro-dimensional fibers employed as suspending a-gents'have an average fiber diameter less than 1 micron and preferably less than 0.75 micron. If the average fiber diameter is above the prescribed maximum or 1.0 micron, the fibers do not impart sufiicient thickening and suspending properties to the vehicle for the maintenance of the powder in a stable gel. It has been found that fibers having an average fiber diameter between 0.01 and 0.5 micron are particularly efiective in maintaining the low atomic weight powdered elements and compounds of such elements in stable suspension in the vehicle.

The micro-dimensional fibers, because of their excellent gelling efficiency, constitute only 0.1 to 3.0 Weight percent of the total gel composition. With micro-dimensional fibers having the preferred average particle diameter between 0.01 and 0.5 micron, glass micro-fiber concentrations of 0.5 to 1.5 weight percent provide adequate gelling and suspending properties to the vehicle for the incorporation of large quantities of powdered material.

The hydrazine-soluble polymeric thickener employed in the composition of the present invention is present in a range of 0.01 to 3.0 weight percent of the entire total gel composition. The soluble polymeric thickeners are added directly to the hydrazine in the form of commercially available powders with agitation until complete solvation has taken place, which is indicated by the formation of a transparent homogenous solution. Examples of these soluble polymers are polyacrylamide, sodium carboxymethylcellulose, hydroxyethyl cellulose, polyvinyl alcohol, sulfonated polyvinyl toluene, sodium polyacrylate and methylpolymethacrylate.

The high energy fuel gel compositions of the present invention are simply prepared by dissolving the prescribed concentration of soluble polymeric thickener material in the hydrazine, agitating the mixture of attain substantially complete dispersion and allowing same to stand until complete solvation has taken place. The prescribed concentration of micro-dimensional fibers is added to the thickened hydrazine and thereafter thoroughly dispersed by mixing means such as by a Waring Blendor, colloid mill or centrifugal wet mill. The powdered element or boron carbide is then slowly added in conventional mixing equipment to the fiber thickened hydrazine until the desired amount of powder is dispersed therein.

The preparation of specific stable gel composition of this invention is illustrated in the following examples:

Example I A base fluid was prepared as follows: 318 g. anhydrous hydrazine (98+%) was weighed int-o a Waring Blendor equipped with a ground :glass cover and 3.2 g. polyacrylamide added. Stirring was begun and continued until a clear solution was obtained. Then 4 grams microglass fiber was added and stirred into the polymer solution. A thick gel was obtained.

Example II grams of aluminum powder, spheroidal in shape, of a particle size of 325 mesh was added slowly with stirring to 20 g. of the base fluid of Example I. There was formed a gel of a soft sticky paste consistency comprising 65.20 weight percent hydrazine, 0.67 weight percent polyacrylamide, 0.8 weight percent micro glass fibers and 33.33 weight percent aluminum powder. There was no settlement of the composition upon standing.

Example III A base fluid was prepared as in Example I except using 200g. hydrazine, 2 grams polyacrylamide and 1 g. microglass fiber were used. A soft fluid paste resulted.

Example IV 10 grams aluminum powder, spheroidal in shape, of a particle size of 325 mesh were added with stirring of 20 g. of the hydrazine gel of Example III. There was formed a fluid paste gel comprising 65.67 weight percent hydrazine, 0.67 'weight percent polyacrylamide, 0.33 weight percent micro glass fibers and 33.33 weight percent aluminum powder. There was slight settlement of the aluminum on standing in this composition.

Example V 10 grams of aluminum powder of flake shape of a particle size of 325 mesh were added slowly with stirring to 20 g. of hydrazine gel of Example III. There was formed a soft paste :gel comprising 66.17 weight percent hydrazine, 0.33 weight percent polyacrylamide, 0.17 weight percent micro glass fibers and 33.33 weight percent aluminum powder. There was no settlement of the composition upon standing.

Example VI 9 g. hydrazine and 9 g. of the gelled hydrazine of Examples III were mixed until homogeneous. 9 grams aluminum powder of spheroidal shape and 3 g. aluminum powder of flake shape both of 325 mesh particle size were added and blended in with stirring. There was formed a gel of very soft paste consistency comprising 59.55 weight percent hydrazine, 0.30 weight percent polyacrylamide, 0.15 weight percent micro glass fibers, 30 weight percent spherical aluminum powder and 10 weight percent flake aluminum powder. There was very slight settlement of composition upon standing.

Example VII 29.5 grams hydrazine containing 1% dissolved polyacrylamide was shaken thoroughly with 0.5 g. cellulose fibers having an average diameter of 0.05 to 0.2 micron to give a very soft paste. 15 grams aluminum powder of spheroidal shape and 5 g. aluminum powder of flake shape, both having a particle size of about 325 mesh, were then added slowly with stirring to the cellulose fiberthickened hydrazine gel. There was formed a gel of a very soft paste consistency comprising 58.4 weight percent hydrazine, 0.60 weight percent polyacrylam-ide, 1.0 weight percent cellulose fiber, 30 weight percent spheroid-al aluminum powder and 10 weight percent flake aluminum powder. There was no apparent settlement of the aluminum powder on standing.

Example VIII 29.9 g. hydrazine containing 3% polyvinyl alcohol was shaken thoroughly with 0.5 g. cellulose fiber having an average diameter of 0:05 to 0.2 microns to give a very soft paste. 15 g. aluminum powder of spheroidal shape and 5 g. aluminum powder of flake shape, both having a particle size of about 325 mesh, were then added slowly with stirring to the cellulose fiber-thickened hydrazine gel. There was formed a gel of very soft paste consistency comprising 57.6 weight percent hydrazine, 1.8 weight percent polyvinyl alcohol, 1.0 weight percent cellulose fiber, 29.7 weight percent spheroidal aluminum powder and 9.9 weight percent flake aluminum powder. There was no apparent settlement of the aluminum powder on standing.

Example IX 29.5 g. hydrazine containing 1 percent dissolved polyacrylamide was shaken thoroughly with 0.5 g. of the cellulose fiber described in the preceding examples. To the resulting soft paste was added 10 g. amorphous boron powder and 5 g. aluminum powder of flake shape, both powder-s being approximately 325 mesh. A soft flowable paste was obtained after thorough mixing comprising 64.9 weight percent hydrazine, 0.7 weight percent polyarcylamide, 1.1 weight percent cellulose fiber, 22.2 weight percent boron and 11.1 weight percent aluminum powder. There was no apparent settlement of the powdered solids on standing.

Example X 29.5 g. hydrazine containing 1 percent dissolved polyacrylamide was shaken with 0.5 g. cellulose fiber as in; Example IX. Then 10 g. mesh boron carbide and 5 g. aluminum powder of flake shape (approx. 325 mesh) were stirred into the blend. A soft flowable paste was; obtained which showed no apparent settlement on stand-- ing. The composition was: hydrazine 64.9 weight per-- cent, cellulose fiber 1.1 weight percent, polyacrylamide- 0.7 weight percent, boron carbide 22.2 weight percent and aluminum powder 11.1 percent.

Example X] 29.5 g. hydrazine containing 1 weight percent dissolved polyacrylamide shaken thoroughly with 0.5 g. of the cellulose fiber described in the preceding examples. To the resultant soft paste is added 15 grams of spheroidal aluminum powder and 5 g. aluminum power of flake shape, both powders being approximately 325 mesh. The softened paste was obtained thereafter through mixing comprising 58.2 weight percent hydrazine, 0.7 weight percent polyacrylamide, 1.0 weight percent cellulose fiber and 40.0

weight percent aluminum. There was no apparent s'et tlement of the powder solids in standing.

Example XII grams of aluminum powder, spheroidal in shape in of aluminum, beryllium, magnesium, carbon, boron,

boron carbide and mixtures thereof, said powder having an average particle size of less than 20 mesh, 0.1 to 3.0 weight percent micro-dimensional fibers having an aver- 5 age fiber diameter less than 1.0 micron, said fibers being Particle 325 mesh Slowly added With Stirring to insoluble and non-reactive with hydrazine, 0.1 to 3.0 318 anhydrous hydlalihe containing 32 of chl'ysotiie weight percent of a hydrazine soluble thickener mateasbestos in the same manner as that in the composition i l d th i de selected from the group con i t. of Example There Was formed a gel of a softened ing of hydrazine and dialkyl substituted hydrazine where- Paste consistency comprising Weight percent hydra 10 in the alkyl group contains from 1 to 3 carbon atoms. Zine, Weight Peicfiht polyacrylamide, Weight P 2. A stable gel as described in claim 1 in which said cent of chl'ysoiile asbestos and 33-33 Weight Percent elemental powder has an average particle size less than aluihihulh P There was 110 Settlement of the 100 mesh and said micro-dimensional fiber is a glass Position from Siahdlhgfiber having an average fiber diameter between 0.01 and Example X111 micron 3. A stable gel as described in 01mm 1 in which said grams of amorphous boron P F 9 a PartlCle dispersed powder is aluminum having an average particle size of 325 mesh was added slowly with stlrring to a base size of 100 to 325 mesh fluid containing l7.7 grams of hydrazine, containing 110% A gel as described in claim 1 in which said powder of Polyacrylamlde and gram of cellulose fiber is boron having an average particle size of 100 to 325 pared in a Waring Blendor. There was formed a gel of mesh 3 h flowable Paste comprising Weight Percent 5. A gel as described in claim 1 in which said elemental drazme 0.66 weight percent polyacrylamide, 1.11 weight powder is a mixture of aluminum and boron having an percent cellulose fiber and 33.33 welght percent amoraverage particle size between 100 and 325 mesh Phous PQ Powder ,There was no Settlement of the 6. A gel as described in claim 1 in which said soluble composltlon p standmg' polymeric thickener material is polyacrylamide.

The foregomg h i demPnsiate the formatlim of 7. A gel as described in claim 1 in which said soluble gel propellants having high speclfic impulses shown in the l k t 1 b th 1 u 1 following Table I by dispersing prescribed low atomic p0 ymencl 1c ener.ma p car 9 y e weight elements and compounds of high energy in liquid ge as described. m clalm 1 m which sald micro hydrazine by the action of polymeric thickener and microdimenslonal fiber l a dimensional fibers. Similarly, high concentrations of gel a descnbed Flalm 1 m whlch Sald mlcro' powdered magnesium can be Suspended in a fib thi k dimenslonal fiber material is a cellulose fiber. ened hydrazine and the resulting gel employed as a flare. A gel Composition as described in Claim 1 in Which In order to demonstrate the usefulness of the above the hydrazine is PhiSent in the range of 46 to Weight compositions the following table shows the specific irnpercent, the hydrazine soluble polymeric thickening mapulse data obtained upon rocket fuels utilizing the proterial is present in the range of 0.3 to 2.0 weight percent, pellents of the present invention: the micro glass fiber is present in the range of 0.3 to 2.0

TABLE I Dispersed Propellant Oxldizer I d I.

CompositionofExample XI LOX 311 1.275 397 In the above Table I abbreviations are presented as weight percent and the elemental powder is present in follows: the range of 10.6 to 5.0 weight percent.

- 11. A gel as described in claim 1 in which micro-dimeni ggg g fggiig sional fiber material is asbestos. Density 5O 12. A gel ashescrrbed in claim in which said ele- I Density impulm mental powder is a mlxture of aluminum and boron carspd bide having an average particle size between 100 and The term aluminum powders when used in present 325 h invention denotes both inhibited and non-inhibited alumi- 13 A Stable gel Comprising 3333 weight percent h hum Powders. When the compositions of the Present ical aluminum powder of 325 mesh, 0.67 weight percent Vention are Subjected to Periods of Storage, it is desir' polyacrylamide, 0.80 weight percent micro-dimensional able to utilize inhibited aluminum powders therein. glass fiber having an average diameter of 0,05 {0 ()2 Accordingly, this invention also involves a process for micron and 510 i h percent h d i incorporating P to 50% y Weight of a metal, a metal 14. A stable gel comprising 33.33 weight percent spherlOid a Compound thereof in hYdfaZihe to form a gel ical aluminum powder of 325 mesh, 0.67 weight percent by thickening the hydrazine with soluble polymeric thickpolyacrylamide, 0 3 weight percent microdimensional v ener and the action of micro-dimensional fibers having an glass fiber having an average diameter of 0.05 to 02 average fiber diameter of less than 1.0 micron in a conmicron and 6557 Weight Percent hydrazine cenihation of to Weight q p of the total com- 15. A stable gel comprising 33.33 weight percent flake posmmi subsequently adding and mlxmg Powder? g aluminum powder of 325 mesh, 0.33 weight percent polyme tan1d or cmlpomds of Such. elements to e eracrylamide, 0.17 Weight percent. micro-dimensional glass thickened hydrazine. The resultlng gels contains 10 to fib h t f O 05 t 02 50 weight percent powder dispersed in suitable form. er avmg average lame 0 O mlcron Using this process 10 to 40 weight percent metal carbide and Welght percent hi such as boron carbide, silicon carbide and titanium car- 70 A Stable gel compnsmg,4( )'o welght Percen? alum! bide can also be suspended in a fiber-thickened hydra- 1mm POW!er 013325 F conslstmg of 15% sphrlcal and zine composition. 25% flake, 0.30 welght percent polyacrylamide, 0.15

We claim: weight percent micro-dimensional glass fiber having an 1 A bl l comprising 10 t 50 weight percent average diameter of 0.05 to 0.2 micron and 59.55 weight powder of an element selected from the group consisting percent hydrazine.

17. A process for suspending 10 to 50 weight percent of a material selected from the group consisting of metals, metalloids and compounds thereof in powder form in a stable gel comprising thickening hydrazine with 0.1 to 3.0 Weight percent of a soluble polymeric thickening material, allowing said thickened hydrazine to stand for a period of time sufficient for solvation to take place, forming a gel by admixing therein 0.1 to 3.0 weight percent of a micro-dimensional glass fiber having an average fiber diameter of less than 1.0 micron, and mixing said powder into said glass fiber-thickened hydrazine to form a stable gel containing 10 to 50 weight percent of said powdered material.

18. A stable gel comprising 33.33 weight percent spheroidal aluminum powder of 325 mesh, 0.67 weight per cent polyacrylamide, 0.8 weight percent micro-dimensional chrysotile asbestos fiber having an average diameter of 0.05 to 0.2 micron and 65.2 weight percent hydrazine.

Journal of the American Rocket Society, No. 72, December 1947, p. 21.

CARL D. QUARFORTH, Primary Examiner.

LEON D. ROSDOL, OSCAR R. VERTIZ, Examiners.

B. R. PADGETT, Assistant Examiner. 

1. A STABLE GEL COMPRISING 10 TO 50 WEIGHT PERCENT POWDER OF AN ELEMENT SELECTED FROM THE GROUP CONSISTING OF ALUMINUM, BERYLLIUM, MAGNESIUM, CARBON, BORON, BORON CARBIDE AND MIXTURES THEREOF, SAID POWDER HAVING AN AVERAGE PARTICLE SIZE OF LESS THAN 20 MESH, 0.1 TO 3.0 WEIGHT PERCENT MICRO-DIMENSIONAL FIBERS HAVING AN AVERAGE FIBER DIAMETER LESS THAN 1.0 MICRON, SAID FIBERS BEING INSOLUBLE AND NON-REACTIVE WITH HYDRAZINE, 0.1 TO 3.0 WEIGHT PERCENT OF A HYDRAZINE SOLUBLE THICKENER MATERIAL AND THE REMAINDER SELECTED FROM THE GROUP CONSISTING OF HYDRAZINE AND DIALKYL SUBSTITUTED HYDRAZINE WHEREIN THE ALKYL GROUP CONTAINS FROM 1 TO 3 CARBON ATOMS. 